Mixed metal alkyl catalyst for olefin polymerization

ABSTRACT

A catalyst composition for use in polymerizing alpha olefins which comprises (a) a solid supported titanium tetrahalide complex, wherein said complex is prepared by contacting a mechanically pulverized solid support with titanium tetrahalide in the absence of mechanical pulverization, and (b) a cocatalyst comprising a mixture of a dialkyl aluminum halide and a dialkyl magnesium compound.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.508,435, filed June 27, 1983 and now U.S. Pat. No. 4,567,154.

BACKGROUND OF THE INVENTION

The present invention relates to a catalyst for use in thepolymerization of alpha olefins. More particularly, the presentinvention relates to a catalyst system comprising a titanium-containingcomponent and a second component comprising a mixture of a dialkylaluminum halide and a dialkyl magnesium compound.

It is known in the art that extremely reactive Ziegler-type catalystscan be prepared by reacting titanium tetrachloride with ethanol in thepresence of a pulverized solid support, such as magnesium chloride.Frequently, esters of aromatic carboxylic acids are included in thispreparation. The resulting solid complex is then mixed with a trialkylaluminum compound, such as tri-isobutyl aluminum, to produce the finalcatalyst. When used to polymerize alpha olefins, these catalysts providehigh yields of stereoregular polymer per part of catalyst. As a result,the catalyst normally does not have to be separated from the polymer togive a final polymer product of specification purity.

Accordingly, U.S. Pat. No. 4,143,223 describes a catalyst compositioncomprising a mechanically pulverized solid halogen-containing titaniumcatalyst component and an organoaluminum compound. The titanium catalystcomponent is obtained by reacting a titanium compound, such as titaniumtetrachloride, with a pulverized solid product derived from a magnesiumcompound, an organic acid ester and an active hydrogen-containingcompound selected from alcohols and phenols.

U.S. Pat. No. 4,107,415 describes a catalyst system comprising acatalyst-forming component which is an addition and/or substitutionproduct of an electron-donor compound (or Lewis base) and an alkylaluminum compound, and a supported catalyst-forming component obtainedby contacting a titanium compound with a carrier which is a mixture ofan active magnesium or manganese dihalide and a solid organic materialwhich is inert to all other catalyst components. The electron-donorcompound is typically an organic acid ester and the inert solid organicmaterial is a compound such as durene, anthracene, acenaphthene ordiphenyl.

Chemical Abstracts, 96:69614c (1982) describes a polymerization catalystcomprising an organic aluminum compound, such as triethyl aluminum, anda solid component obtained by reacting milled mixtures of magnesiumdichloride, aromatic carboxylic acid esters and silicon tetrachloridewith titanium tetrahalide in the presence of chlorinated hydrocarbons,such as dichloroethane.

SUMMARY OF THE INVENTION

The present invention provides a catalyst composition for use inpolymerizing alpha olefins which comprises (a) a solid supportedtitanium tetrahalide complex, wherein said complex is prepared bycontacting a mechanically pulverized solid support with titaniumtetrahalide in the absence of mechanical pulverization, and (b) acocatalyst comprising a mixture of a dialkyl aluminum halide and adialkyl magnesium compound.

Among other factors, the present invention is based on my discovery thata mixed metal alkyl catalyst containing both a dialkyl aluminum halideand a dialkyl magnesium compound is extremely effective in polymerizingalpha olefins to provide highly stereoregular alpha olefin polymers inimproved yield. This is particularly surprising in view of the fact thatalkyl aluminum halides, which are known to form active Zieglercatalysts, by themselves do not provide effective olefin polymerizationcatalysts when mixed with solid supported titanium complexes. Similarly,dialkyl magnesium compounds by themselves do not produce goodpolymerization catalysts when mixed with titanium complexes.

Equally surprising, in view of the prior art teaching, is the discoverythat a mixture of trialkyl aluminum and dialkyl magnesium does not forman active polymerization catalyst with the supported titanium complex.

Furthermore, it has been found that other mixed metal alkyls, such asthe mixture of dialkyl aluminum halide and alkyl zinc or the mixture ofdialkyl aluminum halide and alkyl boron, also provide inactivepolymerization catalysts.

DETAILED DESCRIPTION OF THE INVENTION

The catalyst system of the present invention contains a solid supportedtitanium complex component and a cocatalyst component which comprises amixture of a dialkyl aluminum halide and a dialkyl magnesium compound.

The titanium complex catalyst component may be any of the conventionalsolid titanium-containing complexes used in polymerizing alpha olefins,wherein the titanium is introduced into the complex withoutcopulverization with the support. These titanium-containing catalystcomponents are well known in the art and are described, for example, inthe aforementioned U.S. Pat. No. 4,143,223 and in Chemical Abstracts,96:69614c (1982).

In general, the titanium complexes are obtained by contacting a titaniumcompound with a mechanically pulverized solid support, or carrier, inthe absence of mechanical pulverization. Typically, the titaniumcompound will be a titanium tetrahalide, although other titaniumcompounds are suitable, such as alkoxytitanium halides. The preferredtitanium compound is titanium tetrachloride.

The mechanically pulverized solid support will normally contain amagnesium compound, preferably a magnesium dihalide and more preferably,magnesium dichloride. Other magnesium compounds contemplated includealkoxy magnesium halides, aryloxy magnesium halides, and the like.Manganese dihalides may also be used in place of magnesium dihalides.The magnesium or manganese compounds should preferably be anhydrous.

Additionally, it is preferable to include a carboxylic acid ester in thefinal titanium complex. The carboxylic acid ester may be included aspart of the pulverized solid support or it may be separately added tothe titanium compound. Aromatic carboxylic acid esters are preferred,the most preferred being ethyl benzoate.

Other compounds have been variously described in the literature asuseful in forming the titanium complexes. These compounds includealcohols such as ethanol; phenols such as cresol; and silicontetrachloride. Often these compounds are introduced as part of thepulverized solid support.

The solid support may be mechanically pulverized in a ball mill, avibratory mill, an impact mill, or the like, preferably under dryconditions in the absence of an inert diluent.

As used herein, the term "mechanically pulverized" or "mechanicalpulverization" denotes pulverization which imparts a violent pulverizingeffect to a material and excludes such means as mere mechanicalstirring.

Suitable titanium complexes which are useful for forming the catalyst ofthe present invention include complexes comprising maqnesium dichloride,ethyl benzoate, ethanol and titanium tetrachloride; complexes comprisingmagnesium dichloride, ethyl benzoate, cresol and titanium tetrachloride;and complexes comprising magnesium dichloride, ethyl benzoate, silicontetrachloride and titanium tetrachloride.

The mixed metal alkyl component of the present catalyst comprises amixture of a dialkyl aluminum halide and a dialkyl magnesium compound.The dialkyl aluminum halides which are suitable include dialkyl aluminumhalides, having the empirical formula: AlR₂ X, where R is alkyl and X ishalogen. Generally, the alkyl group will contain from 2 to 8 carbonatoms. Preferred dialkyl aluminum halides are the dialkyl aluminumchlorides. A preferred dialkyl aluminum chloride is diethyl aluminumchloride.

The dialkyl magnesium compounds suitable for use in the catalyst of theinvention are those having alkyl groups of 2 to 8 carbon atoms.Representative examples include dioctyl magnesium, dipropyl magnesium,ethyl propyl magnesium, and the like. A preferred magnesium compound isdibutyl magnesium.

The mixture of the dialkyl aluminum halide and the dialkyl magnesiumcompound has an aluminum to magnesium molar ratio of 1:5 to 5:1,preferably about 2:1. In a preferred embodiment, a small amount of aLewis base is included in the aluminum-magnesium mixture. Usually, fromabout 0.05 to 0.5 moles of Lewis base per mole of total aluminum plusmagnesium are sufficient. Preferred Lewis bases are the carboxylic acidesters, more preferably, the aromatic carboxylic acid esters. Anespecially preferred Lewis base is ethyl benzoate.

The alpha olefins are polymerized in contact with the present catalystsunder conventional polymerization conditions. Polymerization isconducted at temperatures ranging from about 0° C. to 100° C.,preferably from about 20° C. to 70° C. Polymerization pressure isgenerally about 3 to 16 atmospheres, preferably from about 5 to 10atmospheres. The reaction is normally carried out over a period of about1 to 24 hours.

The polymerization can be carried out either in the liquid or gaseousphase. When it is carried out in the liquid phase, an inert organicsolvent can be used as a reaction medium or the olefin itself can beused as the reaction medium. Examples of inert organic solvents includealiphatic hydrocarbons of 4 to 8 carbon atoms such as hexane or heptane;cycloaliphatic hydrocarbons such as cyclohexane; and aromatics such asbenzene, toluene or xylene.

In general, the alpha olefins suitable for use in polymerization includeolefins having from about 2 to 8, preferably 2 to 5, carbon atoms.Typical olefins include ethylene, propylene, 1-butene,4-methyl-1-pentene, 1-hexene, and the like. The present catalyst systemis particularly useful in the polymerization of propylene and 1-butene.

The regulation of the polymer molecular weight during the polymerizationis effected according to known techniques by operating, for instance, inthe presence of hydrogen. The presence of hydrogen as a molecular weightmodifier, operating with the catalysts of the present invention, doesnot appreciably reduce the activity and/or stereospecificity of thecatalysts.

The polymerization can be carried out by any of batchwise,semi-continuous or continuous methods. It is also possible to performthe polymerization in two or more stages under different reactionconditions.

The following examples are provided to illustrate the invention inaccordance with the principles of the invention but are not to beconstrued as limiting the invention in any way except as indicated bythe appended claims.

EXAMPLES

In the following examples, the amount of stereoregular polymer formedwas determined by Soxhlet extraction of the total polymer product over aperiod of 6 hours. An n-heptane solvent was used for polypropylene andan ether solvent was used for poly-1-butene.

The specific viscosity was determined for poly-1-butene using a Decalinsolvent at 115° C. and a concentration of 0.1 g per 100 ml of solvent.The specific viscosity was determined for polypropylene using a Decalinsolvent at 135° C. and a concentration of 0.1 g per 100 ml of solvent.

Abbreviations used in the examples include "Et" for ethyl, "Bu" forbutyl, and "i-Bu" for isobutyl.

EXAMPLE 1

Polymerizations were carried out in a 1-liter, stainless steelautoclave. Before each run, the autoclave was heated to 120° C. for 2hours and cooled to room temperature in dry, oxygen-free nitrogen. Thepropylene (99+%) used was dried over silica gel (Davison Grade 923) andthe n-hexane solvent was dried over molsieve (Linde 1/16 inch pellets,4A). All operations were performed under nitrogen.

The supported titanium complex used in this example was preparedaccording to the procedure described in Chemical Abstracts, 96:69614c(1982). Following this procedure, a mixture of 20 g MgCl₂, 12 ml (12.62g) ethyl benzoate and 3 ml (4.45 g) SiCl₄ was ball milled for 46 hoursto give a fine powder. An 8 g portion of the above powder was mixed with400 ml 1,2-dichloroethane and 40 ml TiCl₄ and heated at 80° C. for 2hours. The resulting complex was filtered, washed with n-hexane anddried in a nitrogen stream to give 5.78 g of catalyst containing 1.90wt. % Ti.

For this example, the autoclave was charged with 163 g n-hexane, 1.4 mMAlEt₂ Cl (25% solution in toluene), 0.7 mM MgBu₂ (0.71 molar inheptane), 0.47 mM ethyl benzoate, and 0.031 g of an MgCl₂ /ethylbenzoate/SiCl₄ /TiCl₄ (Ti=1.90%) catalyst (0.589 mg Ti; 0.0123 mM Ti),prepared as described above, and 125 g liquid propylene. The autoclavewas heated to 50° C. and was maintained at 50° C. for 3 hours. Whennecessary, cooling was applied by an internal water coil. Followingpolymerization, the autoclave was vented and the product was washed withmethanol and dried in vacuum at 70°-80° C. (Alternatively, the polymercould be isolated by evaporation of the solvent.) The polymer yield was118 g, corresponding to 200,300 g polypropylene/g Ti. Propyleneconversion was 94% and the yield of n-heptane insoluble polymer was 92%.The reduced specific viscosity was 4.4 dl/g.

EXAMPLES 2 to 16

Following the procedure of Example 1, 1-butene was polymerized withcatalysts containing a titanium complex of magnesium dichloride, ethylbenzoate, ethanol and titanium tetrachloride, and a cocatalyst mixtureof diethyl aluminum chloride and dibutyl magnesium. The results areshown in Table I. Various trialkyl aluminum cocatalysts are also shownfor comparison.

The supported titanium complex designated "Catalyst A" in Table I wasprepared according to the following procedure. Twenty grams of MgCl₂,6.3 g ethyl benzoate and 15.0 g ethanol was mixed in 100 ml dryn-pentane. The pentane was evaporated and the resulting solid wastransferred into a centrifugal-type ball mill. The solid was ball milledfor 1.5 hours, resulting in a fine powder. A 5 g portion of the abovepowder was mixed with 50 ml TiCl₄ and was heated at 110° C. for 2 hours.The mixture was filtered, an additional 50 ml TiCl₄ was added and themixture was reheated at 110° C. for 2 hours. The resulting complex wasfiltered, washed with hexane and dried in a nitrogen stream to give acatalyst containing 4.12 wt. % Ti. The supported titanium complexdesignated "Catalyst B" in Table I was prepared in a similar manner.

                                      TABLE I                                     __________________________________________________________________________    Polymerization of Pure 1-Butene With AlEt.sub.2 Cl + MgBu.sub.2.sup.a         __________________________________________________________________________                                              Reduced                                                                  Ether                                                                              Specific                                                       Yield     Insoluble                                                                          Viscosity,                          Example                                                                            Catalyst.sup.c                                                                     Cocatalyst.sup.b g   g PB/g Ti                                                                           %    h.sub.sp /C                         __________________________________________________________________________    2    A    AlEt.sub.2 Cl + MgBu.sub.2                                                                     205.4                                                                             78,981                                                                              40.2 2.5                                 3    A    AlEt.sub.2 Cl + MgBu.sub.2 + Et Benzoate                                                       7.2 2,781 91.6 13.7                                4    A    AlEt.sub.2 Cl    0.8 312   --   3.0                                 5    A    MgBu.sub.2       Trace                                                                             --    --   --                                  6    A    AlEt.sub.2 Cl + BEt.sub.3                                                                      Trace                                                                             --    --   --                                  7    A    Al(i-Bu).sub.3   54.1                                                                              20,800                                                                              67.6 5.6                                 8    A    Al(i-Bu).sub.3 + MgBu.sub.2                                                                    Trace                                                                             --    --   --                                  9    A    Al(i-Bu).sub.3 + Et Benzoate                                                                   4.3 1,662 91.2 12.2                                10   A    AlEt.sub.3       Trace                                                                             --    --   --                                  11   A    AlEt.sub.3 + MgBu.sub.2                                                                        Trace                                                                             --    --   --                                  12   B    AlEt.sub.2 Cl + MgBu.sub.2                                                                     237.0                                                                             91,269                                                                              61.4 1.8                                 13   B    AlEt.sub.2 Cl + MgBu.sub.2 + Et Benzoate                                                       229.0                                                                             88,150                                                                              76.0 2.5                                 14   B    Al(i-Bu).sub.3   102.5                                                                             39,438                                                                              82.0 4.1                                 15   B    Al(i-Bu).sub.3 + MgBu.sub.2                                                                    Trace                                                                             --    --   --                                  16   B    Al(i-Bu).sub.3 + Et Benzoate                                                                   125.5                                                                             48,269                                                                              70.2 3.4                                 __________________________________________________________________________    .sup.a 100 ml n-hexane                                                        220 g l-butene   Room temperature,                                            2.6 mg Ti catalyst (0.054 mM)                                                                  1 hour                                                       .sup.b Al--alkyl = 5.60 mM                                                    MgBu.sub.2 = 2.80 mM                                                          Et Benzoate = 1.90 mM (Examples 3, 9)                                         Et Benzoate = 0.32 mM (Examples 13, 16)                                       .sup.c A = MgCl.sub.2 --Et Benzoate-EtOH--TiCl.sub.4 ; Ti = 4.12%;            Centrifugal-type ball mill ground support                                     B = MgCl.sub.2 --Et Benzoate-EtOH--TiCl.sub.4 ; Ti = 1.34%;                   Centrifugal-type ball mill ground support                                 

EXAMPLES 17 to 25

Following the procedure of Example 1, a mixture of 50% 1-butene and 50%2-butene was polymerized with catalysts containing a titanium complex ofmagnesium dichloride, ethyl benzoate, ethanol and titaniumtetrachloride, and a cocatalyst mixture of diethyl aluminum chloride anddibutyl magnesium. The results are shown in Table II. Various trialkylaluminum cocatalysts are also shown for comparison.

The supported titanium complexes designated "Catalyst B" and "CatalystC" in Table II were prepared in a manner similar to that of "CatalystA", described above.

                                      TABLE II                                    __________________________________________________________________________    Polymerization of Mixed-Butene With AlEt.sub.2 Cl + MgBu.sub.2.sup.a          __________________________________________________________________________                                         Ether                                                               Yield     Insoluble                                Example                                                                            Catalyst.sup.c                                                                     Cocatalyst.sup.b g   g PB/g Ti                                                                           %                                        __________________________________________________________________________    17   B    AlEt.sub.2 Cl + MgBu.sub.2                                                                     97.6                                                                              37,538                                                                              40.0                                     18   B    AlEt.sub.2 Cl + MgBu.sub.2 + Et Benzoate                                                       13.4                                                                              5,154 84.4                                     19   B    Al(i-Bu).sub.3   23.2                                                                              8,923 68.6                                     20   C    AlEt.sub.2 Cl + MgBu.sub.2                                                                     92.0                                                                              35,392                                                                              28.4                                     21   C    AlEt.sub.2 Cl + MgBu.sub.2 + Et Benzoate                                                       7.6 2,931 82.4                                     22   C    Al(i-Bu).sub.3   23.6                                                                              9,077 69.2                                     23   C    Al(i-Bu).sub.3 + MgBu.sub.2                                                                    Trace                                                                             --    --                                       24   C    AlEt.sub.3       10.5                                                                              4,027 50.6                                     25   C    AlEt.sub.3 + MgBu.sub.2                                                                        Trace                                                                             --    --                                       __________________________________________________________________________    .sup.a 100 ml n-hexane                                                        220 g mixed-butene                                                                              Room temperature,                                           2.6 mg Ti catalyst (0.054 mM Ti)                                                                1 hour                                                      .sup.b Al--alkyl = 5.60 mM                                                    MgBu.sub.2 = 2.80 mM                                                          Et Benzoate = 0.63 mM                                                         .sup. c B = MgCl.sub.2 --Et Benzoate-EtOH--TiCl.sub.4 ; Ti = 1.34%;           Centrifugal-type ball mill ground support                                     C = MgCl.sub.2 --Et Benzoate-EtOH--TiCl.sub.4 ; Ti = 3.93%; Ball mill         ground support                                                            

EXAMPLES 26 to 36

Following the procedure of Example 1, propylene was polymerized withcatalysts containing a titanium complex of magnesium dichloride, ethylbenzoate, ethanol and titanium tetrachloride, and a cocatalyst mixtureof diethyl aluminum chloride and dibutyl magnesium. The results areshown in Table III. Trialkyl aluminum cocatalysts are also shown forcomparison.

                                      TABLE III                                   __________________________________________________________________________    Polymerization of Propylene With AlEt.sub.2 Cl + MgBu.sub.2.sup.a             __________________________________________________________________________                                               Reduced                                                                 n-Heptane                                                                           Specific                                                       Yield    Insoluble                                                                           Viscosity,                         Example                                                                            Ti Catalyst.sup.c                                                                   Cocatalyst.sup.b g  g PP/g Ti                                                                           %     h.sub.sp /C                        __________________________________________________________________________    26   A     AlEt.sub.2 Cl + MgBu.sub.2                                                                     164.4                                                                            63,250                                                                              58.0  1.6                                27   A     AlEt.sub.2 Cl + MgBu.sub.2 + Et Benzoate                                                       58.4                                                                             22,481                                                                              92.2  7.8                                28   A     AlEt.sub.2 Cl    15.9                                                                             6,131 49.0  2.3                                29   A     Al(i-Bu).sub.3   89.3                                                                             34,338                                                                              42.0  2.3                                30   A     Al(i-Bu).sub.3 + Et Benzoate                                                                   2.6                                                                              996   99.0  Insoluble                          31   C     AlEt.sub.2 Cl + MgBu.sub.2                                                                     158.7                                                                            61,038                                                                              57.2  1.6                                32   C     AlEt.sub.2 Cl + MgBu.sub.2 + Et Benzoate                                                       70.6                                                                             27,154                                                                              92.4  3.0                                33   C     AlEt.sub.2 Cl    18.7                                                                             7,192 44.0  --                                 34   C     Al(i-Bu).sub.3   144.0                                                                            55,385                                                                              45.0  1.4                                35   C     Al(i-Bu).sub.3 + MgBu.sub.2                                                                    7.0                                                                              2,692 64.6  --                                 36   C     Al(i-Bu).sub.3 + Et Benzoate                                                                   42.7                                                                             16,423                                                                              86.6  2.8                                __________________________________________________________________________    .sup.a 100 ml n-hexane                                                                         120 psi propylene,                                           2.6 mg Ti catalyst (0.054 mM)                                                                  50° C., 3 hours                                       .sup.b Al--alkyl = 5.60 mM                                                    MgBu.sub.2 = 2.80 mM                                                          Et Benzoate = 1.90 mM                                                         .sup.c A = MgCl.sub.2 --Et Benzoate-EtOH--TiCl.sub.4 ; Ti = 4.12%;            Centrifugal-type ball mill ground support                                     C = MgCl.sub.2 --Et Benzoate-EtHO--TiCl.sub.4 ; Ti = 3.93%; Ball mill         ground support                                                            

EXAMPLES 37 to 56

Propylene, 1-butene, and a 50/50 mixture of 1-butene and 2-butene werepolymerized following the procedure of Example 1. Various catalysts wereemployed containing a titanium complex and an alkyl aluminum cocatalyst.The results which are shown in Table IV demonstrate the effect ofdibutyl magnesium on various alkyl aluminum cocatalysts. Morespecifically, Table IV shows that dibutyl magnesium activates alkylaluminum halides for olefin polymerization while it completelydeactivates aluminum trialkyls.

                                      TABLE IV                                    __________________________________________________________________________    Effect of MgBu.sub.2 on Al--Alkly Catalysts                                                                              Reduced                                                       Yield           Specific                                                          g Polymer                                                                            Insoluble                                                                          Viscosity,                         Example                                                                            Monomer                                                                              Catalyst*                                                                          Cocatalyst                                                                              g   g Ti   %    h.sub.sp /C                        __________________________________________________________________________    37   l-Butene                                                                             A    AlEt.sub.2 Cl                                                                           0.8 312    --   3.0                                38   l-Butene                                                                             A    AlEt.sub.2 Cl + MgBu.sub.2                                                              205.4                                                                             78,981 40.2 2.5                                39   l-Butene                                                                             B    AlEt.sub.2 Cl + MgBu.sub.2                                                              237.0                                                                             91,269 61.4 1.8                                40   l-Butene                                                                             A    AlEtCl.sub.2                                                                            None                                                                              --     --   --                                 41   l-Butene                                                                             A    AlEtCl.sub.2 + MgBu.sub.2                                                               65.6                                                                              25,246 51.6 2.4                                42   l-Butene                                                                             A    Al(i-Bu).sub.3                                                                          54.1                                                                              20,800 67.6 5.6                                43   l-Butene                                                                             A    Al(i-Bu).sub.3 + MgBu.sub.2                                                             Trace                                                                             --     --   --                                 44   l-Butene                                                                             B    Al(i-Bu).sub.3                                                                          102.5                                                                             39,438 82.0 4.1                                45   l-Butene                                                                             B    Al(i-Bu).sub.3 + MgBu.sub.2                                                             Trace                                                                             --     --   --                                 46   l-Butene                                                                             A    AlEt.sub.3                                                                              Trace                                                                             --     --   --                                 47   l-Butene                                                                             A    AlEt.sub.3 + MgBu.sub.2                                                                 Trace                                                                             --     --   --                                 48   Mixed-Butene                                                                         C    AlEt.sub.2 Cl + MgBu.sub.2                                                              92.0                                                                              35,392 28.4                                    49   Mixed-Butene                                                                         C    Al(i-Bu).sub.3                                                                          23.6                                                                              9,077  69.2                                    50   Mixed-Butene                                                                         C    Al(i-Bu).sub.3 + MgBu.sub.2                                                             Trace                                                                             --     --   --                                 51   Mixed-Butene                                                                         C    AlEt.sub.3                                                                              10.6                                                                              4,027  50.6                                    52   Mixed-Butene                                                                         C    AlEt.sub.3 + MgBu.sub.2                                                                 Trace                                                                             --     --   --                                 53   Propylene                                                                            C    AlEt.sub.2 Cl                                                                           18.7                                                                              7,192  44.0                                    54   Propylene                                                                            C    AlEt.sub.2 Cl + MgBu.sub.2                                                              158.7                                                                             61,038 57.2                                    55   Propylene                                                                            C    Al(i-Bu).sub.3                                                                          144.0                                                                             55,385 45.0                                    56   Propylene                                                                            C    Al(i-Bu).sub.3 + MgBu.sub.2                                                             7.0 2,692  64.6                                    __________________________________________________________________________     *A = MgCl.sub.2 --Et BenzoateEtOH--TiCl.sub.4 ; Ti = 4.12%;                   Centrifugaltype ball mill ground support                                      B = MgCl.sub.2 --Et BenzoateEtOH--TiCl.sub.4 ; Ti = 1.34%; Centrifugaltyp     ball mill ground support                                                      C = MgCl.sub.2 --Et BenzoateEtOH--TiCl.sub.4 ; Ti = 3.93%; Ball mill          ground support                                                           

EXAMPLES 57 to 73

Following the procedure of Example 1, propylene was polymerized usingvarious mixed metal alkyl cocatalysts. The results are summarized inTable V. Table V demonstrates that dialkyl magnesium and alkyl lithiumprovide active cocatalysts when combined with alkyl aluminum halides,whereas other metal alkyls, such as dialkyl zinc and trialkyl boron,give inactive cocatalysts when combined with alkyl aluminum halides.Table V further demonstrates that butyl lithium and dibutyl magnesiumdeactivate the otherwise active trialkyl aluminum cocatalysts.

The preparation of the supported titanium complex used in these examples(MgCl₂ /Et Benzoate/SiCl₄ /TiCl₄ ; Ti=1.90%) is described in Example 1.

                                      TABLE V                                     __________________________________________________________________________    Polymerization of Propylene.sup.a - Effect of Cocatalyst.sup.b                __________________________________________________________________________                                                Reduced                                                                 n-Heptane                                                                           Specific                                                   Yield    Conv.                                                                             Insoluble                                                                           Viscosity,                        Example                                                                            Cocatalyst   (mM)   g  g PP/g Ti                                                                           %   %     h.sub.sp /C                       __________________________________________________________________________    57   AlEt.sub.2 Cl                                                                              (1.4)  10.0                                                                             17,000                                                                              8.0 22.0  1.0                               58   MgBu.sub.2   (0.7)  0.5                                                                              849   0.4                                         59   AlEt.sub.2 Cl/MgBu.sub.2                                                                   (1.4/0.7)                                                                            122.0                                                                            207,100                                                                             98.0                                                                              50.0  1.6                               60   AlEt.sub.2 Cl/Mg(C.sub.6 H.sub.13).sub.2                                                   (1.4/0.7)                                                                            28.0                                                                             47,500                                                                              22.0                                                                              55.0  2.4                               61   AlEt.sub.2 Cl/LiBu                                                                         (1.4/1.4)                                                                            86.0                                                                             146,000                                                                             69.0                                                                              52.0  1.5                               62   AlEt.sub.2 Cl/ZnEt.sub.2                                                                   (1.4/0.7)                                                                            2.0                                                                              3,400 2.0                                         63   AlEt.sub.2 Cl/BEt.sub.3                                                                    (1.4/0.7)                                                                            7.0                                                                              11,900                                                                              6.0       2.3                               64   AlEtCl.sub.2 (1.4)  0.0                                                                              0     0.0 0.0                                     65   AlEtCl.sub.2 /MgBu.sub.2                                                                   (1.4/0.7)                                                                            67.0                                                                             114,000                                                                             54.0                                                                              40.0  1.8                               66   AlEtCl.sub.2 /MgBu.sub.2                                                                   (1.4/1.4)                                                                            23.0                                                                             39,000                                                                              18.0                                                                              59.0  2.2                               67   Al(i-Bu).sub.3                                                                             (1.4)  119.0                                                                            202,000                                                                             95.0                                                                              40.0  1.6                               68   Al(i-Bu).sub.3 /MgBu.sub.2                                                                 (1.4/0.7)                                                                            9.0                                                                              15,300                                                                              7.0 80.0  1.4                               69   Al(i-Bu).sub.3 /Mg(C.sub.6 H.sub.13).sub.2                                                 (1.4/0.7)                                                                            0.0                                                                              0     0.0 0.0                                     70   Al(i-Bu).sub.3 /LiBu                                                                       (1.4/1.4)                                                                            Trace                                                                            Trace --  --    --                                71   AlEt.sub.3   (1.4)  78.0                                                                             132,400                                                                             62.0                                                                              48.0  2.4                               72   AlEt.sub.3 /MgBu.sub.2                                                                     (1.4/0.7)                                                                            5.0                                                                              8,500 4.0       2.7                               73   Al(i-Bu).sub.3 /MgBu.sub.2 /AlEt.sub.2 Cl                                                  (1.4/0.7/1.4)                                                                        99.0                                                                             168,100                                                                             79.0                                                                              40.0  2.1                               __________________________________________________________________________    .sup.a 163 g n-hexane                                                                   50° C.                                                       125 g propylene                                                                         3 hours                                                             .sup.b Catalyst = 0.589 mg Ti (0.0123 mM); MgCl.sub.2 /Et                     Benzoate/SiCl.sub.4 /TiCl.sub.4 ; Ti = 1.90%                              

EXAMPLES 74 to 81

Following the procedure of Example 1, propylene was polymerized withcatalysts containing various supported titanium tetrachloride complexesand mixed metal alkyl cocatalysts. The results are shown in Table VI.Table VI demonstrates the superior performance of the mixed metal alkylcocatalysts, as compared to trialkyl aluminum cocatalysts, when combinedwith a broad range of supported titanium catalysts.

                                      TABLE VI                                    __________________________________________________________________________    Polymerization of Propylene - Catalyst Comparison                                               Ti in                            n-Heptane                       Propylene    Catalyst                                                                           Ti            Time                                                                              Temp.                                                                             Yield Insoluble                  Example                                                                            (99.9+%)                                                                            Catalyst                                                                             %    mg Cocatalyst                                                                           (mM)                                                                              hrs.                                                                              °C.                                                                        g PP/g Ti                                                                           %                          __________________________________________________________________________    74   120 psi                                                                             MgCl.sub.2 /                                                                         3.93 2.59                                                                             AlEt.sub.2 Cl                                                                        5.60                                                                              3   50  27,000                                                                              92                                    Et Benzoate/   MgBu.sub.2                                                                           2.80                                                    EtOH/          Et Benzoate                                                                          1.90                                                    TiCl.sub.4                                                         75   120 psi                                                                             MgCl.sub.2 /                                                                         3.93 2.59                                                                             Al(i-Bu).sub.3                                                                       5.60                                                                              3   50  16,000                                                                              87                                    Et Benzoate/   Et Benzoate                                                                          1.90                                                    Et OH/                                                                        TiCl.sub.4                                                         76   120 psi                                                                             MgCl.sub.2 /                                                                         3.66 0.92                                                                             AlEt.sub.2 Cl                                                                        1.40                                                                              3   50  69,000                                                                              85                                    Et Benzoate/   MgBu.sub.2                                                                           0.70                                                    o-Cresol/      Et Benzoate                                                                          0.47                                                    TiCl.sub.4                                                         77   120 psi                                                                             MgCl.sub.2 /                                                                         3.66 0.92                                                                             Al(i-Bu).sub.3                                                                       1.40                                                                              3   50  32,000                                                                              86                                    Et Benzoate/   Et Benzoate                                                                          0.47                                                    o-Cresol/                                                                     TiCl.sub.4                                                         78   120 psi                                                                             MgCl.sub.2 /                                                                         5.81 0.87                                                                             AlEt.sub.2 Cl                                                                        1.40                                                                              3   50  131,000                                                                             88                                    Et Benzoate/   MgBu.sub.2                                                                           0.70                                                    SiCl.sub.4 /   Et Benzoate                                                                          0.47                                                    TiCl.sub.4                                                         79   120 psi                                                                             MgCl.sub.2 /                                                                         5.81 0.87                                                                             Al(i-Bu).sub.3                                                                       1.40                                                                              3   50  75,000                                                                              92                                    Et Benzoate/   Et Benzoate                                                                          0.47                                                    SiCl.sub.4 /                                                                  TiCl.sub.4                                                         80   Liquid                                                                              MgCl.sub.2 /                                                                         1.90 0.59                                                                             AlEt.sub.2 Cl                                                                        1.40                                                                              3   50  200,000                                                                             92                                    Et Benzoate/   MgBu.sub.2                                                                           0.70                                                    SiCl.sub.4 /   Et Benzoate                                                                          0.47                                                    TiCl.sub.4                                                         81   Liquid                                                                              MgCl.sub.2 /                                                                         1.90 0.59                                                                             Al(i-Bu).sub.3                                                                       1.40                                                                              3   50  120,000                                                                             91                                    Et Benzoate/   Et Benzoate                                                                          0.47                                                    SiCl.sub.4 /                                                                  TiCl.sub.4                                                         __________________________________________________________________________

EXAMPLES 82 to 85

Following the procedure of Example 1, refinery propylene was polymerizedusing a cocatalyst mixture of diethyl aluminum chloride and dibutylmagnesium. The results are summarized in Table VII. A trialkyl aluminumcocatalyst is shown for comparison. Table VII demonstrates the superiorperformance of the mixed metal alkyl cocatalyst, as compared to trialkylaluminum, in polymerizing propylene from a relatively impure refineryfeed.

                                      TABLE VII                                   __________________________________________________________________________    Polymerization of Refinery Propylene.sup.a                                                                                         Reduced                          Cocatalyst                             n-Heptane                                                                           Specific                 Ti.sup.b                                                                              AlEt.sub.2 Cl/MgBu.sub.2 /Et Benzoate                                                        Al(i-Bu).sub.3 /Et Benzoate                                                              Yield    Conv.                                                                             Insoluble                                                                           Viscosity,               Example                                                                            mg mM             mM         g  g PP/g Ti                                                                           %   %     h.sub.sp /C              __________________________________________________________________________    82   0.589                                                                            1.4  0.7  0.47            57 97,000                                                                              46  89    2.8                      83   1.178                                                                            2.8  1.4  0.94            106                                                                              90,000                                                                              85  92    4.0                      84   1.178                                                                            2.8  1.4  1.29            75 63,700                                                                              60  97                             85   1.178             2.8   0.94 56 47,500                                                                              45  94                             __________________________________________________________________________    Analysis of                                                                   Refinery Propylene                                                                                  Component                                                                             %                                               __________________________________________________________________________                          propylene                                                                             57.80                                                                 propane 21.30                                                                 isobutane                                                                             13.10                                                                 n-butane                                                                              0.30                                                                  l-butane                                                                              1.70                                                                  isobutylene                                                                           2.50                                                                  trans-2-butene                                                                        0.45                                                                  cis-2-butene                                                                          0.13                                            __________________________________________________________________________     .sup.a 50° C., 3 hours                                                 51 g nhexane                                                                  216 g refinery propylene (125 g propylene)                                    .sup.b Catalyst = MgCl.sub.2 /Et Benzoate/SiCl.sub.4 /TiCl.sub.4 ; Ti =       1.90%                                                                    

What is claimed is:
 1. A catalyst composition for use in polymerizing alpha olefins which comprises:(a) a solid supported titanium tetrahalide complex, wherein said complex is prepared by contacting a mechanically pulverized solid support with titanium tetrahalide in the absence of mechanical pulverization, and (b) a cocatalyst comprising a mixture of a dialkyl aluminum halide and a dialkyl magnesium compound.
 2. The composition according to claim 1, wherein the cocatalyst comprises a mixture of a dialkyl aluminum chloride and a dialkyl magnesium compound.
 3. The composition according to claim 2, wherein the cocatalyst comprises a mixture of diethyl aluminum chloride and dibutyl magnesium.
 4. The composition according to claim 1, wherein the molar ratio of aluminum to magnesium is 1:5 to 5:1.
 5. The composition according to claim 1, wherein the cocatalyst further comprises a Lewis base.
 6. The composition according to claim 5, wherein the Lewis base is an aromatic carboxylic acid ester.
 7. The composition according to claim 6, wherein the Lewis base is ethyl benzoate.
 8. The composition according to claim 1, wherein the mechanically pulverized solid support comprises a magnesium dihalide, an aromatic carboxylic acid ester and an alcohol or phenol.
 9. The composition according to claim 1, wherein the mechanically pulverized solid support comprises a magnesium dihalide, an aromatic carboxylic acid ester and silicon tetrachloride.
 10. The composition according to claim 8, wherein the titanium tetrahalide is titanium tetrachloride and the mechanically pulverized solid support comprises magnesium dichloride, ethyl benzoate and ethanol.
 11. The composition according to claim 8, wherein the titanium tetrahalide is titanium tetrachloride and the mechanically pulverized solid support comprises magnesium dichloride, ethyl benzoate and cresol.
 12. The composition according to claim 9, wherein the titanium tetrahalide is titanium tetrachloride and the mechanically pulverized solid support comprises magnesium dichloride, ethyl benzoate and silicon tetrachloride. 